The present invention relates to tetraarylethylene compounds. More particularly the present invention relates to substituted tetraaryl compounds, preferably which contain functional groups, most preferably terminal functional groups. Such compounds have the potential to act as molecular xe2x80x9ctemplatesxe2x80x9d for metal complexation. That is, for example, a tetraaryl ethylene compound having at least one, preferably at least two functional substituents on either side of the plane defined by the sigma bonds attached to the ethylenic carbon atoms could form a xe2x80x9csupramolecular assemblyxe2x80x9d comprising alternating layers of a metal atom and the tetraaryl compound.
Chemische Berichte, 1872, 5, 278 reports work by A. Behr to make a substituted tetraphenylethylene. The compound was manufactured from benzophenone and the resulting compounds are hydroxyl substituted in the aromatic (aryl) ring para to the ethylenic carbon atoms. There are a number of subsequent references to this paper, including Kogyo Kagaku Zasshi, 61, 481-2 (1958) by Yoshiro Nakamura, which clearly establishes that the oxidation and subsequent alkylation is para to the ethylenic carbon atoms. The reference fails to clearly teach ortho substituted tetraarylethylenes. Further, the references also fail to teach tetraarylethylene which is substituted both above and below the plane defined by the sigma bonds attached to the ethylenic carbon atoms.
Accordingly, the present invention seeks to provide novel tetraarylethylene compounds.
The present invention provides a compound of formula I: 
wherein at least two R1 are the same and not a hydrogen atom; and R1, R2, R3, R4 and R5 are independently selected from the group consisting of a hydrogen atom; a halogen atom; a hydroxyl radical; a C1-20 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C3-20 allyl radical; a C1-20 alkoxy radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C3-20 allyloxy radical; a carbalkoxy radical of the formula xe2x80x94COOR20 wherein R20 is a hydrogen atom or a C1-20 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a carboxylate radical of the formula xe2x80x94OCOR30 wherein R30 is a C1-20 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C6-10 aryl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C6-10 aryloxy radical or a C7-11 benzyloxy radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; an acyl R6COxe2x80x94 radical wherein R6 is a C1-20 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; an amido radical which is unsubstituted or substituted by up to two C1-20 alkyl radicals; a (xe2x80x94Oxe2x80x94)nxe2x80x94P(R7)2 radical wherein each R7 is independently selected from the group consisting of a C1-20 alkyl radical, a C1-20 alkoxy radical, a C6-10 aryl radical and n is 0 or 1; a (xe2x80x94Oxe2x80x94)nxe2x80x94PO(R8)2 radical wherein each R8 is independently selected from the group consisting of a C1-20 alkyl radical, a C1-20 alkoxy radical, a C6-10 aryl radical and n is 0 or 1; a xe2x80x94Si(R9)3 radical wherein each R9 is independently selected from the group consisting of a C1-20 alkyl radical, a C6-10 aryl radical, a hydrogen radical and an alkoxy radical; a trifluormethanesulfonyloxy radical; or two or more of adjacent substituents R2, R3, R4 and R5 may be taken together to form a fused ring.
The present invention also provides a process for the preparation of a 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetra C1-6 alkoxy)tetraphenylethylene comprising acid catalyzed decomposition of the diazo derivative of 2,2xe2x80x2-di C1-6 alkoxybenzophenone hydrazone at a temperature of less than 25xc2x0 C. in the absence of light.
The present invention also seeks to provide a process for the preparation of 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-4 alkoxy tetraphenylethylene comprising the controlled oxidation of 1,1,2,2,-tetrakis(2xe2x80x2,6xe2x80x2-di C1-6 alkoxyphenyl)ethane. Typically the oxidation takes place in the presence of triphenylmethyl hexafluorophosphate in an inert solvent at low temperatures typically from about 0xc2x0 C. to about 25xc2x0 C. It is believed that the resulting 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-6 alkoxy tetraphenylethylene compound may be dealkylated to 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octahydroxy tetraphenylethylene.
In a further embodiment the present invention provides a process for the preparation of 1,1,2,2-tetrakis(2xe2x80x2,6xe2x80x2-di C1-6 alkoxyphenyl)ethane comprising the radical coupling of bis(2,6-di C1-6 alkoxyphenyl)methanol and bis(2,6-di C1-4 alkoxyphenyl)methane in equimolar amounts in an inert solvent in the presence of p-toluene sulphonic acid.
A second method of preparation of 1,1,2,2-tetrakis(2xe2x80x2,6xe2x80x2-di C1-6 alkoxyphenyl)ethane is provided by the reductive radical coupling of bis(2,6-di C1-6 alkoxyphenyl)methanol using chromous ion (CrCl2) in an acidic medium (HCl).
A further aspect of the present invention provides a process for the synthesis of unsymmetrically substituted tetraphenylethylene compounds of formula 1 wherein two R1 substituents on opposite ends of the central ethylene moiety are C1-20 alkoxy radicals (as defined above) and two R1 substituents on opposite ends of the central ethylene moiety are benzyloxy radicals (as defined above) comprising acid catalyzed decomposition of the diazo derivative of 2-C7-11 benzyloxy, 2xe2x80x2-C1-20 alkoxy benzophenone.
In the diazo-coupling reaction of 2-benzyloxy-2xe2x80x2-methoxybenzophenone hydrazone to give the dibenzyloxydimethoxytetraphenylethylene, both double bond isomers are produced, giving a mixture of E and Zxe2x80x941,2-di(2xe2x80x2-benzyloxyphenyl)-1,2-di(2xe2x80x2-methoxyphenyl)ethane. The subsequent hydrogen resulted in the separable E and Zxe2x80x941,2-di(2xe2x80x2-hydroxyphenyl)-1,2-di(2xe2x80x2-methoxyphenyl)ethylene.
In a further aspect of the present invention the resulting unsymmetrically substituted tetraphenylethylene compounds of formula I wherein two R1 substituents on opposite ends of the central ethylene moiety are C1-20 alkoxy radicals (as defined above) and two R1 substituents on opposite ends of the central ethylene moiety are C7-11 benzyloxy radicals (as defined above) may be subjected to catalytic hydrogenolysis (hydrogenation) to convert the benzyloxy radicals to hydroxyl radicals. Preferably the catalyst is palladium on carbon. Both E and Z isomers can be produced in this way and either separated and used individually or used as a mixture.
In a further embodiment the present invention provides a process for producing compounds of formula I above wherein all R1 substituents are C3-20 allyloxy radicals comprising reacting the compounds of formula I above wherein all R1 substituents are hydroxyl radicals with excess 1-halo C3-20 allyl compound. Preferably the halo substituent is a bromine atom. The resulting compound may be subject to a high temperature Claisen rearrangement to yield the compounds of formula I wherein all R1 substituents are hydroxy radicals and all R2 substituents are C3-20 allyl radicals. The resulting compounds may then be catalytically hydrogenated so that the allyl substituents (R2) are hydrogenated to the corresponding alkane substituents.
In the compounds of the present invention preferably R1, R2, R3, R4 and R5 are independently selected from the group consisting of a hydrogen atom; a halogen atom; a hydroxyl radical; a C1-6 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C3-6 allyl radical; a C1-6 alkoxy radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C3-6 allyloxy radical; a carbalkoxy radical of the formula xe2x80x94COOR20 wherein R20 is a hydrogen atom or a C1-6 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a carboxylate radical of the formula xe2x80x94OCxe2x80x94OR30 wherein R30 is a C1-6 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl atom or a carboxyl atom; a C6-10 aryl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; a C6-10 aryloxy radical or a C7-11 benzyloxy radical which may be unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; an acyl R6COxe2x80x94 radical wherein R6 is a C1-6 alkyl radical which is unsubstituted or substituted by one or more substituents selected from the group consisting of a halogen atom, a hydroxyl radical or a carboxyl radical; an amido radical which is unsubstituted or substituted by up to two C1-6 alkyl radicals; a (xe2x80x94Oxe2x80x94)nxe2x80x94P(R7)2 radical wherein each R7 is independently selected from the group consisting of a C1-6 alkyl radical, a C1-6 alkoxy radical, a C6-10 aryl radical and n is 0 or 1; a (xe2x80x94Oxe2x80x94)nxe2x80x94PO(R8)2 radical wherein each R8 is independently selected from the group consisting of a C1-6 alkyl radical, a C1-6 alkoxy radical, a C6-10 aryl radical and n is 0 or 1; a xe2x80x94Si(R9)3 radical wherein each R9 is independently selected from the group consisting of a C1-6 alkyl radical and a C6-10 aryl radical; and a trifluorosulfonyloxy radical. Preferably R2, R3 and R4 are selected from the group consisting of a hydrogen atom or a lower C1-4 alkyl radical, most preferably a hydrogen atom.
In a particularly preferred embodiment of the present invention, preferably at least two, more preferably up to four of the R1 substituents are independently selected from the group consisting of hydroxyl radicals; alkoxy radicals; aryloxy radicals; carboxyl radical; a (xe2x80x94Oxe2x80x94)nxe2x80x94P(R7)2 radical wherein each R7 is independently selected from the group consisting of a C1-6 alkyl radical, a C1-6 alkoxy radical, a C6-10 aryl radical and n is 0 or 1; and a trifluorosulfonyloxy radical. In a further preferred embodiment of the present invention at least two, most preferably up to four of the R1 and at least two, most preferably up to four, of the R5 radicals are independently selected from the group consisting of hydroxyl radicals; alkoxy, preferably C1-6 radicals; a (xe2x80x94Oxe2x80x94)nxe2x80x94P(R7)2 radical wherein each R7 is independently selected from the group consisting of a C1-6 alkyl radical, a C1-6 alkoxy radical, a C6-10 aryl radical and n is 0 or 1; and aryloxy, preferably C6-10 radicals; and a trifluoromethanesulfonyloxy radical. Preferably at least two and most preferably all four R1 subsitituents are the same. Preferably at least two and most preferably all four R5 substituents are the same. In a further aspect of the present invention all the R1 substituents are the same and all the R5 substituents are the same. In the above embodiments R1 and R5 are as described above.
Some of the compounds of the present invention may be prepared by the acid catalyzed decomposition of a diazo compound of formula II: 
wherein R11 and R12 are independently selected from the group consisting of a C1-6 alkyl radical and a C6-10 aryl radical, preferably a C1-4 alkyl radical or a benzyl radical.
In one embodiment of the present invention, R11 and R12 are the same and are C1-6, most preferably C1-4 alkyl radicals, preferably methyl radicals (a symmetrically substituted compound). In another embodiment of the invention, R11 is a C1-6, most preferably a C1-4 alkyl radical, preferably a methyl radical; and R12 is a C6-10 benzylic radical, preferably benzyl (i.e. an unsymmetrically substituted compound).
A suitable acid is anhydrous p-toluene sulphonic acid. The reaction is carried out at low temperatures, typically less than 25xc2x0 C., in the absence of light or heat. In the case where R11 and R12 are the same and an alkyl radical, the resulting product is 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetraalkoxy)tetraphenylethylene. Preferably, the alkyl substituent is a C1-4 alkyl radical, most preferably methyl. In the case where R11 is an alkyl radical and R12 is a benzyl radical, the resulting product is a mixture of E and Zxe2x80x941,2-di(2xe2x80x2-benzyloxyphenyl)-1,2-di(2xe2x80x2-methoxyphenyl)ethylene.
In a further embodiment of the invention the mixture of unsymmetrically substituted E and Zxe2x80x941,2-di(2xe2x80x2-benzyloxyphenyl)-1,2-di(2xe2x80x2-methoxyphenyl)ethylene compounds may further be catalytically hydrogenolyzed at the benzyloxy substituents to produce separable E and Zxe2x80x941,2-di(2xe2x80x2-hydroxyphenyl)-1,2-di(2xe2x80x2-methoxyphenyl)ethylene compounds (i.e. the compounds of formula I wherein two R1 substituents at opposite ends of the central ethylene moiety are hydroxyl radicals and two R1 substituents at opposite ends of the central ethylene moiety are methoxy radicals).
The hydrogenolysis may be carried out in the presence of hydrogen under moderate pressure, from about 100 to 1000, preferably from about 300 to 600 psi (689.5xc3x97103 Pa to 6.895xc3x97103 kPa, preferably from about 2.068xc3x97103 kPa to 20.685xc3x97103 kPa).
The diazo starting material may be prepared by the oxidation of a compound of formula III: 
wherein R11 and R12 are as defined in formula II. If R11 and R12 are the same and a C1-6 alkyl radical, the compound (formula III), is a 2,2xe2x80x2-C1-6 alkoxybenzophenone hydrazone or a 2,2xe2x80x2-C1-6 alkoxy benzhydrylidene-hydrazine. If R11 is a C1-6 alkoxy radical and R12 is a benzyl radical the compound is a 2-benzyloxy-2xe2x80x2-alkoxybenzophenone hydrazone or a 2-benzyloxy-2xe2x80x2-alkoxybenzhydrylidene-hydrazine. As noted above, preferably the alkyl radical is a methyl radical and if present the benzyl radical is unsubstituted. Preferred starting materials are 2,2xe2x80x2-dimethoxybenzophenone hydrazone or 2,2xe2x80x2-dimethoxybenzhydrylidene-hydrazine, and 2-benzyloxy-2-methoxybenzophenone hydrazone or 2-benzyloxy-2-methoxybenzhydrylidene-hydrazine.
The oxidation may be carried out in the present of nickel peroxide. Care must be taken with this oxidation. The reaction should be carried out at low temperatures, preferably 0xc2x0 C. or less (e.g. an ice-salt bath) and the reaction should be protected from light which will decompose the diazo product.
The compound of formula III may be prepared by the reaction of a compound of formula IV: 
wherein R11 and R12 are as defined above with hydrazine monohydrate (at high temperature).
For the symmetrically substituted compounds the starting 2,2xe2x80x2-dialkoxy benzophenone may be prepared by metallation of anisole with n-butyllithium in a suitable solvent such as diethylether/tetramethylethylenediamine and subsequent quenching with N,N-dimethylcarbamoyl chloride or by methylation of commercially available 2,2xe2x80x2-dihydroxybenzophenone using excess methyl iodide and sodium hydroxide in a highly polar organic solvent (e.g. dimethyl sulfoxide (DMSO)).
For the unsymmetrically substituted compounds, the symmetrically substituted alkoxy compound is prepared and one of the alkoxy groups is converted to an unsymmetrically substituted 2-hydroxy-2xe2x80x2-methyloxybenzophenone in the presence of boron trichloride at a temperature from xe2x88x9265xc2x0 C. to 25xc2x0 C. The resulting 2-hydroxy-2xe2x80x2-methyloxybenzophenone is then benzylated using benzyl bromide in the presence of potassium carbonate to yield 2-benzyloxy-2xe2x80x2-methoxybenzophenone. Alternative reaction routes would be known or derivable to those skilled in the art.
Once the 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetraalkoxy)tetraphenylethylene is prepared, the alkoxy groups may be de-alkylated to the tetra hydroxyl derivative. For example, 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetramethoxy)tetraphenylethylene may be demethylated using boron tribromide at low temperatures to produce the tetra hydroxyl derivative. Additionally, the 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetrahydroxy)tetraphenylethylene may be further treated, for example, with compounds such as anhydrides of C1-6 carboxylic acids such as acetic anhydride in pyridine to produce 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetraacetoxy)tetraphenylethylene and with trifluoromethanesulfonic anhydride to produce 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetrakis(trifluorosulfonyloxy)tetraphenylethylene.
The 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-(tetrahydroxy)tetraphenylethylene may also be reacted with a C3-20, preferably a C3-6 allylating agent such as a 1-halo C3-20, preferably a C3-6 allyl compound. The resulting 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetra C3-20, preferably C3-6 allyloxy tetraphenylethylene may then be heated to cause a Claisen rearrangement resulting in a 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetrahydroxy-3,3xe2x80x2,3xe2x80x3,3xe2x80x2xe2x80x3-tetra C3-20, preferably C3-6, allyl tetraphenylethylene which may then be hydrogenated as described above to yield a 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetrahydroxy-3,3xe2x80x2,3xe2x80x3,3xe2x80x2xe2x80x3-tetra C3-30, preferably C3-6 alkyl tetraphenylethylene. The simplest allylating agent is allylbromide (1-bromo-2-propene) yielding sequentially as described above 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetra(allyloxy)tetraphenylethylene (or 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetra(2-propenyloxy)tetraphenylethylene); 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetrahydroxy-3,3xe2x80x2,3xe2x80x3,3xe2x80x2xe2x80x3-tetra(allyl)tetraphenylethylene (or 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetrahydroxy-3,3xe2x80x2,3xe2x80x3,3xe2x80x2xe2x80x3-tetra(2-propenyl)tetraphenylethylene); and 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3-tetrahydroxy-3,3xe2x80x2,3xe2x80x3,3xe2x80x2xe2x80x3-tetra(n-propyl)tetraphenylethylene, respectively.
Other reaction schemes and methods of altering the substituents are well known to those skilled in the art. For example, the hydroxy derivative could be esterified using common acid chlorides and anhydrides or phospharylated using common chlorophosphines (ClPRn2) or chlorophosphates (ClP(O)Rn2). Further, the trifluorosulphenylate derivative may be transformed using palladium catalyzed substitution using appropriate carbon, nitrogen, phosphorus and oxygen nucleaphiles.
In a further embodiment of the present invention the 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-6 alkoxy tetraphenylethylene (also tetrakis(2,6-di C1-6 alkoxyphenyl)ethylene) compound may be prepared by the controlled oxidation of a compound of formula V: 
(2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-6 alkoxy tetraphenylethane (also tetrakis(2,6-di C1-6 alkoxyphenyl)ethane) wherein R13 is a C1-6, preferably a C1-4 alkoxy radical, most preferably methoxy or ethoxy. Most preferably all R13 radicals are the same. One method for the controlled oxidation of the compound is by reaction with triphenylmethylhexafluorophosphate in an inert solvent such as dichloromethane. The reaction may be carried out at temperatures from 0xc2x0 C. to 25xc2x0 C.
The resulting 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-6 alkoxy tetraphenylethylene (also tetrakis(2,6-di C1-6 alkoxyphenyl)ethylene) compounds may then be subjected to dealkylation to yield 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octahydroxyphenylethylene. The dealkylation has been described above. One method for dealkylation is to treat the 2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-6 alkoxy tetraphenylethylene (also tetrakis(2,6-di C1-6 alkoxyphenyl)ethylene) compound with boron tribromide at temperatures from 0xc2x0 C. to 25xc2x0 C.
The resulting 2,2xe2x80x2,2xe2x80x3,2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octahydroxyphenylethylene compound may be treated as described above (for example acetoxylation or allylated and subsequently subjected to a rearrangement reaction) to yield further derivatives as described above.
The compounds of formula V (2,2xe2x80x2,2xe2x80x3,2xe2x80x2xe2x80x3,6,6xe2x80x2,6xe2x80x3,6xe2x80x2xe2x80x3-octa C1-6 alkoxy tetraphenylethane (also tetrakis(2,6-di C1-6 alkoxyphenyl)ethane) may be prepared by the radical coupling of a compound of formula VI: 
(bis(2,6-di C1-6 alkoxyphenyl)methanol) wherein R13 is as defined above with a compound of formula VII: 
(bis(2,6-di C1-4 alkoxyphenyl)methane) wherein R13 is as defined above, in an inert solvent in the presence of p-toluene sulphonic acid.
A second method for generation of 1,1,2,2-tetrakis(2xe2x80x2,6xe2x80x2-di C1-6 alkoxyphenyl)ethane is by the reductive radical dimerization of compound (VI) using chromous chloride and hydrochloric acid in acetone solution. The products of these two coupling methods are rotational isomers, each with distinct chemical reactivity.
The compounds of formula VI may be prepared by metallation of a compound of formula VIII: 
wherein R13 is as defined above with n-butyllithium in an inert solvent, preferably diethyl ether/tetramethylenediamine solution, followed by quenching with ethyl formate.
The compounds of formula VII above may be prepared by reducing the compounds of formula VI above for example by treatment with stoichometric amounts of p-toluenesulfonic acid in a mixture of acetonitrile and tetrahydrofuran.
The present invention will now be illustrated by the following non-limiting examples in which unless otherwise indicated parts means parts by weight (e.g. grams) and per cent means weight per cent.
A stirred suspension of 2,2xe2x80x2-dimethoxybenzophenone (20.72 g, 0.0855 mol) and 20 mL (0.412 mol) of hydrazine monohydrate in 25 mL of 1-butanol was heated to reflux overnight. After cooling to room temperature the two phase reaction mixture was poured into water and cooled to induce crystallization. The white precipitate was filtered, washed with water and petroleum ether and dried in vacuo to yield 2,2xe2x80x2-dimethoxybenzophenone hydrazone (1).